Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$86.40	3.723%	$89.6167	$89.62	$89.60	$89.60
Purchase #2	$185.30	13.259%	$209.8689	$209.87	$209.85	$209.90
Purchase #3	$88.30	7.212%	$94.6682	$94.67	$94.65	$94.70
Purchase #4	$221.38	3.266%	$228.6103	$228.61	$228.60	$228.60
Purchase #5	$240.72	8.430%	$261.0127	$261.01	$261.00	$261.00
Purchase #6	$50.92	10.103%	$56.0644	$56.06	$56.05	$56.10
Purchase #7	$168.95	12.722%	$190.4438	$190.44	$190.45	$190.40
7 purchase totals =	$1,041.97		$1,130.2850	$1,130.28	$1,130.20	$1,130.30